1. Field of Invention
The invention relates to the technology for an optical identification, and more particularly to a two dimensional optical identification (2D-OID) with the same gray level in a visual aspect, and a printing product using the same.
2. Related Art
With the progress of the technology, the message identifier (ID) technique is getting more and more progressed. The message identifier mainly employs a computer to automatically acquire features or build-in data of objects according to differences between the objects, and converts the acquired features or data into the digital information that can be stored in the computer system. Then, the objectives of identification and management can be achieved according to the comparison and the data management of the computer system. The message identifier technique includes a barcode, a magstripe, optical character recognition (OCR), biometric recognition, a smart card and radio frequency identification (RFID). The applications thereof are very wide and include checkout, credit cards, fingerprint recognition, telephone IC cards and easy cards for metro.
An optical identification (OID) can hide the digital data and acquire the hidden digital data in the typical printing product, and can hide the digital data in the typical printing product through the standard printing program and the standard ink. The data previously hidden in the printing product can be taken out through the optical and image processing techniques of an optical recognition pen (OID Pen). In the prior art, each OID coded graph is composed of many fine dots each corresponding to one set of specific values. The OID has the high privacy.
However, the most difficult portion in the coding technique is that the coded graph needs to have the dots that are uniformly distributed so that the visual interference can be effectively reduced and the glory of the printing product cannot be influenced.